The fault diagnosis device for performing a fault diagnosis of a vehicle uses a technique, in which the actuator in the vehicle is forcefully operated for monitoring purpose when a diagnosis detection condition is satisfied. In such case, how the diagnosis of a certain diagnosis item has been performed is measured and monitored as a diagnosis rate, i.e., the number of diagnoses performed per trip counts, regarding which a trip is counted as a period between a start of the vehicle's power (e.g., an engine) and the next start.
Further, the minimum requirement rate is set by regulations as the diagnosis rate of certain diagnosis items, e.g., the regulated minimum requirement rate of 0.336 means that, the subject diagnosis item has to be diagnosed at least 336 times in 1000 trips.
The minimum requirement rate is set mostly for the system diagnosis items. The detection condition of the system diagnosis items tends to have many assumptions, that means prerequisites or in-advance “must conditions”, such as an engine rotation number and/or an opening degree of a throttle valve have to be in a specific range continuously for a certain period of time, which may sometimes be very difficult to satisfy, depending on how the vehicle/engine is driven.
Further, the diagnosis items with the regulated minimum requirement rate may increase in the future, and new or different diagnosis detection conditions that are more difficult to satisfy may be added. Furthermore, developing countries may newly adopt the regulations enforcing the minimum requirement rate for many diagnosis items. That is, the diagnosis may be more difficult to complete, in terms of achieving the minimum requirement rate for various diagnosis items.
In the above-described technique, a forceful operation of an actuator suitably enables diagnosis of certain diagnosis items. However, the satisfaction of the diagnosis detection condition(s) is not controlled in the above-described technique, i.e., the satisfaction is situation dependent, precarious, or is left in happy-go-lucky manner. That is, the satisfaction of the diagnosis detection condition(s) by the above-described technique may become more difficult in the future.
The following patent documents are listed as an example of the above-described technique.
(Patent document 1) JP 2004-164601 A
(Patent document 2) WO 2008/038741